An input signal that consists of a series of narrow repetitive pulses is often difficult to detect visually with a conventional oscilloscope. The pulses appear as a series of spikes whose duration and shape are not easily determined without complicated manual adjustment of the vertical gain, sweep speed, display position, and triggering point. Such adjustment of an oscilloscope often requires an operator who is thoroughly familiar with the controls of the particular model at hand. However, the engineer or technician faced with the task may only use an oscilloscope infrequently. For such an occasional user, making the necessary adjustments to permit accurate viewing of the pulse is a time-consuming and difficult task.
Recognizing this problem inherent in operation of oscilloscopes, designers have added an "auto-setup" feature that automatically adjusts the amplitude and sweep speed of the oscilloscope to display a predetermined range of signal cycles. Typically two to five cycles are shown depending on the signal frequency simply by pushing an appropriately labeled button. Although this feature expands somewhat the display of a narrow pulse, this display may be inadequate for detailed observation. For instance, if the pulse portion of the signal has a duty factor of less than 1%, setting up this display via the auto-setup feature will result in a display of a pulse duration that is less than 0.5% of the full screen. The pulse portion of the display would therefore still be too narrow to be viewed with any detail.
The invention overcomes this limitation of the "auto-setup" feature by magnifying the horizontal display of a narrow pulse of less than a predetermined duty factor to fill a substantial portion of the oscilloscope screen, regardless of the initial narrowness of the pulse.